#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>

#define NLOOP 5000
int     counter;                /* incremented by threads */

void   *doit(void *);

int main ( int argc, char **argv )
{
     pthread_t tidA, tidB;
     pthread_create(&tidA, NULL, &doit, NULL);
     pthread_create(&tidB, NULL, &doit, NULL);
     /* wait for both threads to terminate */
     pthread_join(tidA, NULL);
     pthread_join(tidB, NULL);
     exit(0);
 }

 void * doit(void *vptr) {
      int    i, val;
      /*
       * Each thread fetches, prints, and increments the counter NLOOP times.
       * The value of the counter should increase monotonically.
       */
      for (i = 0; i < NLOOP; i++) {
          val = counter;
          printf("%u: %d\n", (unsigned int) pthread_self(), val + 1);
          counter = val + 1;
      }
      return (NULL);
 }
